1. Field of Invention
This invention relates to a blood flow volume measurement method and a vital sign monitoring apparatus and in particular to a blood flow volume measurement method of measuring the blood flow volume ejected by cardiac contraction in vital sign monitoring apparatus and a vital sign monitoring apparatus.
2. Related Art
In medical facilities, variation in the hemodynamics of a patient in an operating room, an intensive care unit, an emergency treatment room, artificial dialysis treatment room, etc., needs to be monitored continuously as much as possible.
Hitherto, the variation in the hemodynamics of such a patient has been monitored mainly by monitoring the blood pressure directly.
In a living body, the cardiac output and the systemic vascular resistance are adjusted so that the blood pressure of the center is limited within a certain range. Therefore, to know the variation in the hemodynamics of a patient at an early stage, it is not enough to only monitor the blood pressure directly, and when change in the blood pressure is observed, the cause of the change in the blood pressure needs to be known. Then, in addition to change in the blood pressure, change in the cardiac output needs to be monitored.
As a method of measuring the change in the cardiac output to monitor the variation in the hemodynamics of a patient, methods are used as described below such as a thermo dilution method, a dye dilution method, and an ultrasound method.
First, the thermo dilution method will be discussed.
In the thermo dilution method a Swan-Ganz catheter is inserted through a jugular vein, a given amount of cooled saline or cooled glucose solution is poured to a central vein or a right atrial, and the cardiac output is measured from temperature change in a pulmonary artery.
Recently, another thermo dilution method of measuring the cardiac output from temperature change caused by blood warmed through a catheter has also been available; according to this method, the cardiac output can be measured automatically every given time.
Next, the dye dilution method will be discussed.
In the dye dilution method, a given amount of dye is poured through a vein, and the dye concentration is measured invasively or non-invasively in the part where the dye is uniformly diluted to a constant concentration, and the cardiac output is measured.
Next, the ultrasound method will be discussed.
The ultrasound method is a method of measuring the inner diameter of an arterial blood vessel such as a descending aorta and the blood flow velocity using ultrasound transesophageally, thereby the cardiac output is measured.
Aforementioned methods measuring cardiac output for monitoring the variation in the hemodynamics of a patient in the related arts involve the following problems:
The thermo dilution method involves a problem of intermittent measurement and incapability of continuous measurement. Inserting a catheter in the thermo dilution method is highly invasive for a patient and involves a possible danger of infection, etc.
Further, the thermo dilution method is a method requiring a skilled medical person for measurement and inserting a catheter.
Recently, a continuous measurement method has also been developed in the thermo dilution method, but the method requires insertion of a catheter and the above-described problem cannot be solved.
The dye dilution method also involves a problem of incapability of continuous measurement and requires a skilled medical person.
The ultrasound method imposes a burden of stress on a patient because a transducer is attached transesophageally.
Recently, a non-invasive measurement from the body surface has also been available as a kind of the ultrasound method, but continuous measurement is impossible.
Considering requirement for an advanced skill of medical person and an invasive procedure for a patient, the methods described above cannot continuously be conducted easily and it is difficult to monitor the variation in the hemodynamics of a patient continuously at all times by the methods.
It is therefore an object of the invention to provide a vital sign monitoring apparatus and a method of measuring the blood flow volume ejected by cardiac contraction in a vital sign monitoring apparatus capable of non-invensively monitoring the variation in the hemodynamics of a patient continuously at all times.
According to a first aspect of the present invention, there is provided a blood flow volume measurement method of measuring a blood flow volume ejected by cardiac contraction in a vital sign monitoring apparatus, the blood flow volume measurement method comprising the steps of calculating estimated systolic blood pressure and estimated diastolic blood pressure from information relevant to blood pressure successively measured based on the relationship between information relevant to blood pressure and systolic blood pressure and the relationship between information relevant to blood pressure and diastolic blood pressure, successively measuring a systolic duration and a diastolic duration, and calculating a blood flow volume ejected by cardiac contraction based on the estimated systolic blood pressure and the estimated diastolic blood pressure successively calculated and the systolic duration and the diastolic duration successively measured.
Since the estimated systolic blood pressure and the estimated diastolic blood pressure are thus calculated from the information relevant to blood pressure measured (non-invensively) successively, the variation in the hemodynamics of a patient can be monitored non-invensively continuously at all times. Further, a skilled medical person for inserting a catheter, etc., is not required.
According to a second aspect of the present invention, there is provided a blood flow volume measurement method of measuring a blood flow volume ejected by cardiac contraction in a vital sign monitoring apparatus, the blood flow volume measurement method comprising the steps of calculating estimated systolic blood pressure and estimated diastolic blood pressure from information relevant to blood pressure successively measured based on the relationship between information relevant to blood pressure and systolic blood pressure and the relationship between information relevant to blood pressure and diastolic blood pressure, calculating an estimated systolic duration and an estimated diastolic duration of an aorta from a systolic duration and a diastolic duration of a peripheral blood vessel successively measured based on the relationship between the systolic or diastolic duration in the aorta and the systolic or diastolic duration in the peripheral blood vessel, and calculating a blood flow volume ejected by cardiac contraction based on the estimated systolic blood pressure, the estimated diastolic blood pressure, the estimated systolic duration, and the estimated diastolic duration successively calculated.
The systolic or diastolic duration in the aorta is thus measured intermittently, whereby the estimated systolic blood pressure and the estimated diastolic blood pressure can be corrected, so that more accurate estimates can be provided.
According to a third aspect of the present invention, there is provided a blood flow volume measurement method of measuring a blood flow volume ejected by cardiac contraction in a vital sign monitoring apparatus, the blood flow volume measurement method comprising the first step of measuring a predetermined systolic pulse wave area in an aorta, measuring a systolic duration or a diastolic duration in the aorta, and measuring first blood flow volume based on the predetermined systolic pulse wave area and the systolic duration or the diastolic duration, the second step of calculating estimated systolic blood pressure and estimated diastolic blood pressure from information relevant to blood pressure successively measured based on the relationship between information relevant to blood pressure and systolic blood pressure and the relationship between information relevant to blood pressure and diastolic blood pressure at the same time as the first blood flow volume is measured, and further measuring a systolic duration and a diastolic duration, the third step of determining a predetermined coefficient in a predetermined relational expression so that blood flow volume calculated according to the predetermined relational expression from the estimated systolic blood pressure, the estimated diastolic blood pressure, the systolic duration, and the diastolic duration successively calculated at the second step matches the first blood flow volume measured at the first step, the fourth step of calculating estimated systolic blood pressure and estimated diastolic blood pressure from information relevant to blood pressure successively measured based on the relationship between information relevant to blood pressure and systolic blood pressure and the relationship between information relevant to blood pressure and diastolic blood pressure, the fifth step of successively measuring a systolic duration and a diastolic duration, and the sixth step of calculating a blood flow volume based on the estimated systolic blood pressure and the estimated diastolic blood pressure successively calculated and the systolic duration and the diastolic duration successively measured according to the predetermined relational expression using the predetermined coefficient determined at the third step.
The systolic pulse wave area and the systolic duration or the diastolic duration in the aorta are thus measured intermittently, whereby the estimated systolic blood pressure and the estimated diastolic blood pressure can be corrected, so that furthermore accurate estimates can be provided.
The blood flow volume measurement method according to a fourth aspect of the present invention, the fifth step successively calculates an estimated systolic duration and an estimated diastolic duration of an aorta from a systolic duration and a diastolic duration of a peripheral blood vessel successively measured, based on the relationship between the systolic or diastolic duration in the aorta and the systolic or diastolic duration in the peripheral blood vessel.
Since the relationship between the systolic or diastolic duration in the aorta and the systolic or diastolic duration in the peripheral blood vessel is thus previously found, the values of the aorta can be successively estimated from the measurement values of the peripheral blood vessel successively measured.
The blood flow volume measurement method according to a fifth aspect of the present invention, the step of calculating the blood flow volume calculates the cardiac output per unit time using a heart rate or a pulse rate successively measured.
Thus, the cardiac output (CO) can be found based on the heart rate (HR) successively measured or can be found based on the pulse rate (PR) successively measured.
The blood flow volume measurement method according to a sixth aspect of the present invention, the relationship between information relevant to blood pressure and systolic blood pressure and the relationship between information relevant to blood pressure and diastolic blood pressure are determined by the information relevant to blood pressure measured at blood pressure measuring time with a cuff and the systolic blood pressure and the diastolic blood pressure measured by blood pressure measurement with the cuff.
Thus, the information relevant to blood pressure, the systolic blood pressure, and the diastolic blood pressure can be measured with the cuff at the same time.
The blood flow volume measurement method according to a seventh aspect of the present invention, the information relevant to blood pressure is a value relevant to pulse wave propagation measured using electrocardiogram measurement means and photoelectric pulse wave detection means attached to a periphery.
Since the information is thus measured using the electrocardiogram measurement means and the photoelectric pulse wave detection means attached to the periphery of a patient, it can be measured non-invensively and successively.
The blood flow volume measurement method according to an eighth aspect of the present invention, the systolic or diastolic duration in the aorta is measured from a pulse wave detected by cuff pulse wave detection means for blood pressure measurement, and that the systolic or diastolic duration in the peripheral blood vessel is measured from a pulse wave detected by photoelectric pulse wave detection means attached to a periphery.
Thus, the systolic or diastolic duration in the aorta is measured by the cuff pulse wave detection means and the systolic or diastolic duration in the peripheral blood vessel is measured by the photoelectric pulse wave detection means.
The blood flow volume measurement method according to a ninth aspect of the present invention, the predetermined systolic pulse wave area in the aorta is calculated from a pulse wave detected by cuff pulse wave detection means for blood pressure measurement.
Thus, the systolic pulse wave area is calculated from the pulse wave detected by the cuff pulse wave detection means.
The blood flow volume measurement method according to a tenth aspect of the present invention further comprises the step of calibrating the relationship between the estimated systolic blood pressure, the estimated diastolic blood pressure, the systolic duration, and the diastolic duration based on which the blood flow volume is calculated at the step of calculating the blood flow volume and the blood flow volume according to the blood flow volume measured by an apparatus for measuring blood flow volume that can be used for another calibration.
Since an apparatus for measuring the blood flow volume that can be used for another calibration is thus used, calibration accuracy is more improved.
The blood flow volume measurement method according to an eleventh aspect of the present invention, the information relevant to blood pressure is a pulse wave propagation time or a pulse wave propagation velocity.
Thus, the pulse wave propagation time or the pulse wave propagation velocity can be used as the information relevant to blood pressure.
According to a twelfth aspect of the present invention, there is provided a vital sign monitoring apparatus comprising estimated blood pressure calculation means for calculating estimated systolic blood pressure and estimated diastolic blood pressure from information relevant to blood pressure successively measured based on the relationship between information relevant to blood pressure and systolic blood pressure and the relationship between information relevant to blood pressure and diastolic blood pressure, systolic and diastolic duration measurement means for successively measuring a systolic duration and a diastolic duration, and blood flow volume calculation means for calculating a blood flow volume ejected by cardiac contraction based on the estimated systolic blood pressure and the estimated diastolic blood pressure successively calculated and the systolic duration and the diastolic duration successively measured.
According to the configuration, since the estimated systolic blood pressure and the estimated diastolic blood pressure are calculated from the information relevant to blood pressure measured (non-invensively) successively, the variation in the hemodynamics of a patient can be monitored non-invensively continuously at all times. Further, a skilled medical person for inserting a catheter, etc., is not required.
The vital sign monitoring apparatus according to a thirteenth aspect of the present invention further comprises input means for externally inputting values for calibrating the relationship between the estimated systolic blood pressure, the estimated diastolic blood pressure, the systolic duration, and the diastolic duration based on which the blood flow volume calculation means calculates the blood flow volume, and the blood flow volume.
According to the configuration, the calibration values can be input externally through the input means.
The vital sign monitoring apparatus according to a fourteenth aspect of the present invention further comprises alarm output means for outputting an alarm when the blood flow volume successively calculated by the blood flow volume calculation means changes beyond a predetermined threshold value.
According to the configuration, when the blood flow volume changes beyond the predetermined threshold value, an alarm can be output.
The vital sign monitoring apparatus according to a fifteenth aspect of the present invention, the alarm output means outputs the contents containing an instruction notifying to calibrate the relationship between the estimated systolic blood pressure, the estimated diastolic blood pressure, the systolic duration, and the diastolic duration based on which the blood flow volume calculation means calculates the blood flow volume, and the blood flow volume.
According to the configuration, a calibration instruction alarm can be output.
According to a sixteenth aspect of the present invention, there is provided a blood flow volume measurement method of measuring a blood flow volume ejected by cardiac contraction in a vital sign monitoring apparatus, the blood flow volume measurement method comprising the steps of, based on the relationship between blood pressures at different levels and information relevant to blood pressure, calculating estimated blood pressures at the different levels from the successively measured information relevant to blood pressure, successively measuring a systolic duration and a diastolic duration, and calculating a blood flow volume based on the estimated blood pressure successively calculated and the systolic duration and the diastolic duration successively measured.
Since the estimated blood pressures at the different levels are thus calculated from the successively (non-invensively) measured information relevant to blood pressure, the variation in the hemodynamics of a patient can be monitored non-invensively continuously at all times. Further, a skilled medical person for inserting a catheter, etc., is not required.
According to a seventeenth aspect of the present invention, there is provided a blood flow volume measurement method of measuring a blood flow volume ejected by cardiac contraction in a vital sign monitoring apparatus, the blood flow volume measurement method comprising the steps of, based on the relationship between blood pressures at different levels and information relevant to blood pressure, calculating estimated blood pressures at the different levels from the successively measured information relevant to blood pressure, calculating an estimated systolic duration and an estimated diastolic duration of an aorta from a systolic duration and a diastolic duration of a peripheral blood vessel successively measured based on the relationship between the systolic or diastolic duration in the aorta and the systolic or diastolic duration in the peripheral blood vessel, and calculating a blood flow volume based on the estimated systolic blood pressure, the estimated diastolic blood pressure, the systolic duration, and the diastolic duration successively calculated.
Thus, since the estimated blood pressures at the different levels are calculated from the successively (non-invensively) measured information relevant to blood pressure, and further the systolic or diastolic duration of the aorta is estimated from successively measured the systolic or diastolic duration of peripheral vessel based on the relationship between the systolic or diastolic duration of the aorta and the systolic or diastolic duration of peripheral vessel, more accurate calculation of blood flow volume can be provided.
According to an eighteenth aspect of the present invention, there is provided a blood flow volume measurement method of measuring a blood flow volume ejected by cardiac contraction in a vital sign monitoring apparatus, the blood flow volume measurement method comprising the first step of measuring a predetermined systolic pulse wave area in an aorta, measuring a systolic duration or a diastolic duration in the aorta, and measuring first blood flow volume based on the predetermined systolic pulse wave area and the systolic duration or the diastolic duration, the second step of, based on the relationship between blood pressures at different levels and information relevant to blood pressure, calculating estimated blood pressures at the different levels from the successively measured information relevant to blood pressure at the same time as the first blood flow volume is measured, and further measuring a systolic duration and a diastolic duration, the third step of determining a predetermined coefficient in a predetermined relational expression so that blood flow volume calculated according to the predetermined relational expression from the estimated systolic blood pressure, the estimated diastolic blood pressure, the systolic duration, and the diastolic duration successively calculated at the second step matches the first blood flow volume measured at the first step, the fourth step of calculating estimated systolic blood pressure and estimated diastolic blood pressure from information relevant to blood pressure successively measured based on the relationship between blood pressures at different levels and information relevant to blood pressure, the fifth step of successively measuring a systolic duration and a diastolic duration, and the sixth step of calculating a blood flow volume based on the estimated systolic blood pressure and the estimated diastolic blood pressure successively calculated and the systolic duration and the diastolic duration successively measured according to the predetermined relational expression using the predetermined coefficient determined at the third step.
The systolic pulse wave area and the systolic duration or the diastolic duration in the aorta are thus measured intermittently, whereby the estimated systolic blood pressure and the estimated diastolic blood pressure can be corrected, so that furthermore accurate estimates can be provided.
The blood flow volume measurement method according to an nineteenth aspect of the present invention, any two of systolic blood pressure, diastolic blood pressure, mean blood pressure, end systolic blood pressure, mean systolic blood pressure, or mean diastolic blood pressure are used as the blood pressures at the different levels.
Two of the blood pressures at the different levels, the difference between which has statistically good correlation with the blood flow volume ejected by cardiac contraction, can be used.
The blood flow volume measurement method according to a twenty aspect of the present invention, the information relevant to blood pressure is information relevant to pulse wave propagation time.
Thus, the information relevant to the pulse wave propagation time can be used as the information relevant to blood pressure.